In non-implant edentulous patients reduction of height and width of residual alveolar ridge and reduced attached KT compromise the denture-bearing area unambiguously leading to decrease in full denture stability and retention. Furthermore, in implant edentulous patients insufficient KT is associated with increased plaque accumulation, tissue inflammation, soft tissue recession, marginal bone loss and increased prevalence of peri-implantitis. The present study aimed to evaluate keratinized tissue gain and the wound contraction rate between apically positioned flap without and with free gingival graft strip over a 6-month follow up period.

This research was designed as split mouth controlled clinical study included 17 patients having edentulous upper jaw with reduced width of keratinized tissue ( ≤ 4mm measured from middle of the crest to the buccal mucogingival junction or ≤ 2mm from occluso-buccal edge of the alveolar ridge to the mucogingival junction). In each patient, both surgical techniques, apically positioned flap without and with free gingival graft strip, were applied simultaneously. The change of keratinized tissue width and wound contraction rate were measured 30, 60 , 90 and 180 days after surgery

The surgical procedure was done by one experienced surgeon. Before surgery, patients were given to rinse the mouth with 0,12% clorhexidine gluconate for 1 minute. Following the local anesthesia utilizing Artikaine 4% with 1:100000 epinephrine the elevation of split-thickness flap was started. Incision was done at the level of MGJ from maxillary tuberosity on one side to tuberosity of the opposite side. Initially, sharp dissection was carefully done in an apical direction to leave exposed periosteum without tearing. Further, blunt dissection was used to advance periosteum exposure and muscle fibres detachment. For apically positioned flap group the split thickness flap was apically positioned as much as possible and sutured to the periosteum utilizing T-mattress sutures. Regarding free gingival graft strip group, after the split thickness flap was sutured apically, free gingival graft in the form of strip, harvested from the palate, was sutured to the apical end of the recipient bed leaving the rest of periosteum to heal by secondary epitelization. Free gingival graft strip stabilized with 6-0 resorbable sutures by means of two single interrupted and cross-mattress sutures. The dimensions of free gingival graft strip was 30-35mm in length (depending on the length of the apical part of recipient bed), 2-3mm in width and 1-1.5mm in thick. The palatal donor site was sutured using cross-mattress sutures. Patients were given postoperative instructions which included antibiotics regime (amoxicillin 500mg, 3x1 for 5 days or in case of penicillin allergy- clindamycin 600mg, 2x1 5 days) and rinsing with chlorehexidine solution 0.12% two times a day for 14 days.

To control for bias, measurements were carried out by one examiner not involved in the surgical procedure. Measurements were taken from regions representing tooth #16 to tooth #26. The colour-coded periodontal probe (University of North Caroline Probe CP15 PCPUNC156, Hy Friedy) utilized to measure the distance from depth of newly formed vestibule to the edge of vertical cut made on the GM representing position of certain tooth. Measurement for each tooth were summarized in three regions: anterior group (central and lateral incisor region)- AG, middle group (canine, first and second premolar region)- MG and posterior group (first molar region)- PG.

First measurement was done immediately after surgery (T0) and represented the distance from depth of newly formed vestibule to the edge of vertical cut made on the GM (for apically positioned flap group) and from apical margin of free gingival graft strip to the edge of vertical cut made on the GM (for free gingival graft strip group). Follow up measurements were taken at 30 (T1), 60 (T2) , 90 (T3) and 180 (T4) days after surgery.

Primary outcome was wound contraction rate representing the percentage of keratinized tissue reduction between time point immediately after surgery (T0, 100%) and follow-up time points (T1,T2,T3 and T4). Secondary outcomes were 1) patient-reported outcomes such as patient discomfort and pain which was evaluated utilizing visual analogue scale (VAS) at 1, 2, 7 and 10 days after surgery and the amount of ibuprofen taking within 10 days after surgery, 2) the surgery time which represented the time from first incision to the last suture with a digital timer rounded to the whole minutes, 3) wound infection (yes/no), and wound bleeding (yes/no).

Inclusion Criteria:

• patients with edentulous upper jaws which are not able to wear full upper denture owing to compromise retention and stability being 18 years old or older,
• patients with reduced width of keratinized tissue (≤ 4mm) measured from middle of the crest to the buccal mucogingival junction ( the distance from occluso-buccal edge of the alveolar ridge to the mucogingival junction ≤ 2mm), - patients who belong to ASA1 or ASA2, according to the American Academy to Anesthesiology
• patients who do not suffer from any systemic disease affecting wound healing,
• patients which are able to provide a signed informed consent and are able to comply with determined follow-up time points.

Exclusion Criteria:

• patient is a heavy smoker (more than 10 cigarettes per day),
• patients with history of malignancy, radiotherapy or chemotherapy within the 5 years,
• pregnant or nursing patients,
• patients who are taking medications which have an effect on mucosal healing in general (steroids, non-steroidal anti-inflammatory drugs taken in high doses and in long term, bisphosphonates).